Apparatus and method for monitoring the position of an orthopaedic prosthesis

ABSTRACT

A system, apparatus, and method for determining a position of an orthopaedic prosthesis includes a patient support platform, a sensor array coupled to the patient support platform, and a controller electrically coupled to the sensor array. The sensor array is configured to generate data signals in response to an output signal of a signal source(s) coupled to the orthopaedic prosthesis and/or a bone of the patient. The controller is configured to determine a position of the orthopaedic prosthesis and/or the bone of the patient based on the data signals.

TECHNICAL FIELD

The present disclosure relates generally to systems and methods forpost-operatively monitoring the position of an orthopaedic prosthesis.

BACKGROUND

Orthopaedic implants or prostheses are implanted in patients byorthopaedic surgeons to, for example, correct or otherwise alleviatebone and/or soft tissue loss, trauma damage, and/or deformation of thebone(s) of the patients. Over time, the position of the orthopaedicprosthesis may change. For example, the orthopaedic prosthesis maymigrate from the original implant location and/or subside into thesupporting bony anatomy. In some cases, migration of the orthopaedicprosthesis may be an early indicator of implant loosening. As such,post-operative monitoring of the position of the orthopaedic prosthesismay provide an indication of potential difficulties that may developover time.

SUMMARY

According to one aspect, an apparatus for monitoring the position of anorthopaedic prosthesis may include a patient support platform. Thepatient support platform may be configured to support a patient in astanding position. In some embodiments, the patient support platform maybe embodied as an enclosure having an interior space defined therein.The apparatus may also include a sensor array coupled to the patientsupport platform. The sensor array may be configured to generate datasignals in response to an output signal received from a signal sourcecoupled to the orthopaedic prosthesis. In some embodiments, the signalsource may be embodied as one or more magnetic sources. In suchembodiments, the sensor array may include a plurality of magneticsensors. The magnetic sensors may be configured to generate data signalsin response to a magnetic field generated by the magnetic source(s). Inother embodiments, the signal source may be embodied as one or morewireless transmitters. In such embodiments, the sensor array may includea plurality of antennas configured to generate data signals in responseto an output signal received from the wireless transmitter(s). Theplurality of antennas may include, for example, a plurality of firstantennas positioned substantially coplanar with each other and at leastone second antenna positioned non-coplanar with respect to the pluralityof first antennas. The antennas may be, for example, spiral directionalantennas. In such embodiments, the plurality of first antennas may bepositioned such that a boresight of each first antenna is directedtoward a common volume of space and the second antenna may be positionedsuch that a boresight of the second antenna is directed toward thecommon volume of space.

The apparatus may also include means for securing at least a portion ofthe patient's body in a fixed position relative to the sensor arraywhile the patient is supported by the patient support platform. Themeans for securing the patient may include, for example, one or morepads coupled to a support frame of the apparatus and movable withrespect to the support frame to secure at least a portion of the patientin a fixed position relative to the patient support platform. Theapparatus may also include a controller electrically coupled to thesensor array. In embodiments wherein the patient support platform isembodied as an enclosure, the controller or portion thereof may bepositioned in the enclosure. The controller may be configured todetermine a position of the orthopaedic prosthesis based on the datasignals received from the sensor array. To do so, in some embodiments,the controller may be configured to determine the position of theorthopaedic prosthesis by comparing the data signals to each other. Theapparatus may further include a display device coupled to the patientsupport platform and electrically coupled to the controller. In suchembodiments, the controller may be configured to display indicia of thelocation of the orthopaedic prosthesis on the display device. Thecontroller may also be configured to retrieve position data indicativeof a previously determined position of the orthopaedic prosthesis from astorage device and display indicia of the previously determined positionof the orthopaedic prosthesis on the display device.

According to another aspect, a system for monitoring the position of anorthopaedic prosthesis may include a patient support platform. Thepatient support platform may be configured to support the patient in astanding position. The system may also include a first signal sourceconfigured to be coupled to the orthopaedic prosthesis and generate afirst output signal when the patient is standing on the patient supportplatform. The first signal source may be, for example, a magnetic sourceor a wireless transmitter. The apparatus may also include a sensor arraycoupled to the patient support platform. The sensor array may beconfigured to generate data signals in response to the first outputsignal received from the first signal source. In embodiments wherein thesignal source is embodied as one or more magnetic sources, the sensorarray may be embodied as a number of magnetic sensors. In embodimentswherein the signal source is embodied as one or more wirelesstransmitters, the sensor array may be embodied as a plurality ofantennas. In such embodiments, the plurality of antennas may include aplurality of first antennas each being positioned substantially coplanarwith each other and at least one second antenna positioned non-coplanarwith respect to the plurality of first antennas.

The system may also include a controller. The controller may beelectrically coupled to the sensor array. The controller may beconfigured to determine a present position of the orthopaedic prosthesisbased on the data signals received from the sensor array. For example,the controller may be configured to determine the location of theorthopaedic prosthesis with respect to the patient support platform. Thecontroller may also be configured to retrieve position data indicativeof a previously determined position of the orthopaedic prosthesis from astorage device. Additionally, the controller may be configured todisplay indicia of the present position and the previously determinedposition of the orthopaedic prosthesis on a display device. In someembodiments, the system may further include a second signal sourceconfigured to be coupled to a first component of the orthopaedicprosthesis and generate a second output signal when the patient isstanding on the patient support platform. In such embodiments, the firstsignal source may be configured to be coupled to a second component ofthe orthopaedic prosthesis. The controller may be configured todetermine the position of the first component and the second componentof the orthopaedic prosthesis with respect to each other based on datasignals received from the sensor array in response to the first and thesecond output signals. In another embodiment, the second signal sourcemay be configured to be coupled to a bone of the patient. In suchembodiments, the controller may be configured to determine the positionof the bone of the patient and the orthopaedic prosthesis with respectto each other based on data signals received from the sensor array inresponse to the first and the second output signals.

According to a further aspect, an apparatus for monitoring the positionof an orthopaedic prosthesis may include a patient support platformconfigured to support a patient in a standing position. The apparatusmay also include a support frame coupled to the patient support platformand a display device coupled to the support frame. Additionally, theapparatus may include a plurality of pads coupled to the support frame.The plurality of pads may be movable with respect to the support frameto secure at least a portion of the patient in a fixed position. Theapparatus may also include a sensor array coupled to the support frame.The sensor array may be configured to generate data signals in responseto an output signal received from a signal source coupled to theorthopaedic prosthesis. In some embodiments, the signal source may beembodied as one or more magnetic sources. In such embodiments, thesensor array may include a plurality of magnetic sensors. In otherembodiments, the signal source may be embodied as one or more wirelesstransmitters. In such embodiments, the sensor array may include aplurality of antennas. The apparatus may further include a controllerelectrically coupled to the sensor array. The controller may beconfigured to determine a position of the orthopaedic prosthesis basedon the data signals received from the sensor array and display indiciaof the position of the orthopaedic prosthesis on the display device. Insome embodiments, the apparatus may also include a display devicecoupled to the support frame and electrically coupled to the controller.In such embodiments, the controller is configured to display indicia ofthe location of the orthopaedic prosthesis on the display device.Additionally, in such embodiments, the controller may be configured toretrieve position data indicative of a previously determined position ofthe orthopaedic prosthesis from a storage device and display indicia ofthe previously determined position of the orthopaedic prosthesis on thedisplay device.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a simplified diagram of a system for monitoring the positionof an orthopaedic prosthesis;

FIG. 2 is a perspective view of one embodiment of a patient supportapparatus of the system of FIG. 1;

FIG. 3 is a perspective view of another embodiment of the patientsupport apparatus of the system of FIG. 1;

FIG. 4 is an elevation view of one embodiment of a securing device forsecuring a patient in a fixed position on the patient support apparatusof FIG. 1;

FIG. 5 is a simplified flowchart of one embodiment of an algorithm fordetermining a position of an orthopaedic prosthesis executed by thesystem of FIG. 1;

FIG. 6 is a simplified flowchart of another embodiment of an algorithmfor determining a position of an orthopaedic prosthesis executed by thesystem of FIG. 1; and

FIG. 7 is a simplified flowchart of a further embodiment of an algorithmfor determining a position of an orthopaedic prosthesis executed by thesystem of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Referring to FIG. 1, a system 10 for monitoring the position of anorthopaedic prosthesis 12 includes a patient support apparatus 14configured to support a patient 16 thereon. The patient supportapparatus 14 includes a patient support platform 18 and a support frame20. The patient support platform 18 may be embodied as any type ofplatform having a generally planar surface 22 (see FIGS. 2 and 3)capable of supporting the patient 16 in a standing position. As such,the patient support platform 18 may be formed from any material capableof supporting the patient 16 such as, for example, a non-ferrousmetallic material, a plastic material, wood, or the like. The supportframe 20 is coupled to the patient support platform 18 and provides astructure for the patient 16 to grasp and/or hold during the operationof the system 10. In addition, the support frame 20 provides a structureto which other components of the apparatus 14 may be coupled asdescribed below. The support frame 20 may have any configuration basedon, for example, characteristics of the intended patients, the numberand type of components included in the apparatus 14, the particularimplementation of the apparatus 14, and/or the like. In someembodiments, the support frame 20 may be adjustable to accommodatepatients of different heights, movability, and the like.

The apparatus 14 also includes a display device 24 and a sensor array 26coupled to the support frame 20. The display device 24 may be embodiedas any device capable of displaying images and information to thepatient 16 and/or an orthopaedic healthcare provider such as anorthopaedic surgeon or nurse. In one particular embodiment, the displaydevice 24 is embodied as a display monitor such as a liquid crystaldisplay (LCD) monitor. The sensor array 26 may be embodied as any deviceor collection of devices capable of sensing, receiving, or otherwisedetecting output signals from one or more signal sources 28 coupled toone or more components of the orthopaedic prosthesis 12 and/or a bone(s)of the patient 16. In one embodiment, as discussed in more detail belowin regard to FIG. 2, the signal source(s) 28 is embodied as a number ofmagnetic sources such as permanent magnets. In such embodiments, thesensor array 26 is embodied as a number of magnetic sensors configuredto sense a magnetic field generated by the magnetic source(s) andgenerate data signals indicative of a position of the magnetic source(s)relative to the sensor array 26. In another embodiment, as discussed inmore detail below in regard to FIG. 3, the signal source(s) 28 isembodied as a number of wireless transmitters. In such embodiments, thesensor array 26 is embodied as a number of antennas configured toreceive output signals of the wireless transmitters and generate datasignals indicative of a position of the wireless transmitter(s) relativeto the sensor array 26.

It should be understood that, as used herein, the term “position” isintended to refer to any one or more of the six degrees of freedom whichdefine the location and orientation of a body in space relative to apredetermined reference point or other body. For example, the positionof a body may be defined by an X-coordinate value, a Y-coordinate value,a Z-coordinate value, a first rotational value about the X-axis, asecond rotational value about the Y-axis, and/or a third rotationalabout the Z-axis value of the body relative to a predetermined referencepoint or other body. For example, the orthopaedic prosthesis 12 and/orbone of the patient 16 may have a position defined by one or more of theabove-described six degrees of freedom values relative to the sensorarray 26, the patient support platform 18, or the patient supportapparatus 14.

The patient support apparatus 14 also includes a controller 30communicatively coupled to the sensor array 26 via a number ofcommunication links 32 and to the display 24 via a number ofcommunication links 34. The communication links 32, 34 may be embodiedas any type of communication links capable of facilitating electricalcommunication between the controller 30 and the sensor array 26 and thedisplay 24, respectively. For example, the communication links 32, 34may be embodied as any number of wires, cables, or the like.

The controller 30 includes a processor 36 and a memory device 38. Theprocessor 36 may be embodied as any type of processor including, forexample, discrete circuitry (e.g., a collection of logic devices),general purpose integrated circuit(s), and/or application specificintegrated circuit(s) (i.e., ASICs). The memory device 48 may beembodied as any type of memory device and may include one or more memorytypes, such as, random access memory (i.e., RAM) and/or read-only memory(i.e., ROM). In addition, the controller 30 may include other devicesand circuitry typically found in a computer or computing device forperforming the functions described herein such as, for example, a harddrive, input/output circuitry, and/or the like.

In use, the controller 30 receives data signals from the sensor array 26indicative of the position of the signal source(s) 28 while the patient16 is supported by the patient support platform 18. The controller 30 isconfigured to determine the position (e.g., the location andorientation) of the orthopaedic prosthesis 12 and/or bones of thepatient to which the signal source(s) 28 is/are coupled based on thedata signals. The controller 30 may use any suitable algorithm todetermine the position of the orthopaedic prosthesis and/or bone of thepatient. For example, as discussed in more detail below in regard toFIG. 2, the controller 30 may be configured to determine the position ofthe orthopaedic prosthesis 12 and/or bones of the patient by performingan optimization algorithm on the data signals received from the sensorarray 26 in those embodiments wherein the signal source(s) 28 areembodied as magnetic sources and the sensor array 26 is embodied as amagnetic sensor array. Alternatively, as discussed in more detail belowin regard to FIG. 3, the controller 30 may be configured to determinethe position of the orthopaedic prosthesis 12 and/or bones of thepatient by using a radio frequency (RF) direction finding algorithm inthose embodiments wherein the signal source(s) 28 are embodied aswireless transmitters and the signal array 26 is embodied as a pluralityof antennas.

Additionally, depending on the particular application, the controller 30may be configured to determine the position of the orthopaedicprosthesis 12 and/or bones of the patient relative to a predeterminedcoordinate system. For example, in some embodiments, the controller 30may be configured to determine the position of the orthopaedicprosthesis 12 with respect to the patient support apparatus 14 (e.g.,the patient support platform 18) as discussed in more detail below inregard to FIG. 5. In such embodiments, the change of the location and/ororientation of the orthopaedic prosthesis 12 relative to the patientsupport apparatus 14 may be monitored over time. Alternatively, inembodiments wherein a signal source 28 is coupled to each relevantcomponent of an orthopaedic prosthesis 12 (e.g., a signal source 28 maybe coupled to a tibial component and a femoral component of a kneeprosthesis), the controller 30 may be configured to determine theposition of each component of the orthopaedic prosthesis 12 with respectto each other as discussed in more detail below in regard to FIG. 6. Insuch embodiments, the change in relative position between the componentsmay be monitored over time. Further, in embodiments wherein a signalsource 28 is coupled to one or more components of the orthopedicprosthesis 12 and one or more signal sources 28 are coupled to a bone ofthe patient 16, the controller 30 may be configured to determine theposition of the orthopaedic prosthesis 12 (or component thereof) and therelevant bone(s) of the patient with respect to each other as discussedin more detail below in regard to FIG. 7. In such embodiments, thechange in relative position between the orthopaedic prosthesis 12 andthe relevant bone of the patient 16 may be monitored over time.Regardless, once the controller 30 has determined the position of theorthopaedic prosthesis 12 and/or bone(s) of the patient 16, thecontroller 16 may be configured to display indicia of the position ofthe prosthesis 12 and/or bones, such as images, graphs, symbols, or thelike, on the display device 24 such that the position may be viewed bythe patient 16 and/or an orthopaedic healthcare provider.

It should be appreciated that the orthopaedic prosthesis 12 may beembodied as any type of orthopaedic prosthesis formed from any number oforthopaedic prosthesis components. For example, the orthopaedicprosthesis 12 may be embodied as a knee prosthesis, a hip prosthesis, ashoulder prosthesis, an ankle prosthesis, or any other joint replacementprosthesis as well as any type of orthopaedic trauma implant such as aplate, nail, or the like. As discussed above, one or more of thecomponents of the orthopaedic prosthesis may include a signal source 28coupled thereto. For example, in those embodiments wherein theorthopaedic prosthesis 12 is embodied as a knee prosthesis, the tibialcomponent and/or the femoral component of the orthopaedic prosthesis 12may include a signal source 28 coupled thereto. As such, it should beappreciated that the system 10 is usable with any type of orthopaedicprosthesis capable of having a suitable signal source 28 coupled to oneor more components thereof.

In the illustrative embodiment of FIG. 1, the controller 30 is coupledto or otherwise housed in the patient support apparatus 14. For example,in some embodiments, the patient support platform 18 is embodied as anenclosure having an interior chamber or space. In such embodiments, thecontroller 30, or portion thereof, may be housed in the interior chamberor space of the patient support platform 18. Alternatively, thecontroller 30, or portion thereof, may be located remotely from thepatient support platform 30 and/or apparatus 14.

In some embodiments, the system 10 may also include a remote database40. The database 40 may be embodied as any type of database, electroniclibrary, and/or file storage location. For example, the database 40 maybe embodied as a structured database or as an electronic file folder ordirectory containing a number of separate files and an associated“look-up” table. Further, the database 40 may be stored on any suitabledevice. For example, the database 40 may be stored in a set of memorylocations of a remote computer and/or a stored on a separate storagedevice such as a hard drive or the like.

The database 40 is communicatively coupled to the controller 30 via anumber of communication links 42. The communication links 42 may beembodied as any type of communication links capable of facilitatingelectrical communication between the controller 30 and database 40. Forexample, the communication links 42 may be embodied as any number ofwires, cables, or the like. Additionally, the communication links 42 mayform a portion of a communication network such as, for example, a LocalArea Network (LAN), a Wide Area Network (WAN), and/or a global,publicly-accessible network such as the Internet.

In use, the controller 30 may be configured to store position dataindicative of the determined position of the orthopaedic prosthesis 12and/or bones of the patient in the database 40. Additionally, in someembodiments, the controller 30 may be configured to retrieve historicalposition data (i.e., data indicative of the position of the orthopaedicprosthesis 12 and/or bones of the patient as determined during a priorexamination of the patient using the system 10). In such embodiments,the controller 30 may also be configured to display indicia of thepreviously determined positions of the prosthesis 12 and/or bones, suchas images, graphs, symbols, or the like, on the display device 24. Ifso, such indicia of the previously determined positions may be displayedcontemporaneously with the indicia indicative of the present position ofthe orthopaedic prosthesis 12 and/or bones of the patient such that acomparison between the present positions and the historical position(s)may be performed by an orthopaedic healthcare provider.

The system 10 may also include a remote control panel 44 in someembodiments. The control panel 44 may be located remotely from theapparatus 14 such as in a separate room of a healthcare facility orotherwise apart from the patient support apparatus 14. The remotecontrol panel 44 is communicatively coupled to the controller 30 via anumber of communication links 50. The communication links 50 may beembodied as any type of communication links capable of facilitatingelectrical communication between the controller 30 and remote controlpanel 44. For example, the communication links 50 may be embodied as anynumber of wires, cables, or the like.

The control panel 44 may be used by an orthopaedic healthcare provider,such as an orthopaedic surgeon, to control the operation of the patientsupport apparatus 14. To do so, the orthopaedic healthcare provider mayoperate an input device 46 of the remote control panel 44 to supplyinformation, directions, and/or responses to the controller 30 via thecommunication links 50. For example, the orthopaedic healthcare providermay instruct the controller 30 when the measurement process should begin(e.g., when the patient has successfully mounted the patient supportplatform 18). Additionally, the controller 30 may be configured todisplay indicia of the determined position of the orthopaedic prosthesis12 and/or bone(s) of the patient 16, as well as indicia of anypreviously determined positions retrieved from the database 40, on thedisplay device 48 via the communication links 50. In this way, anorthopaedic healthcare provider may operate the apparatus 14 and monitordata determined by the controller 30 using the remote control panel 44.

Referring now to FIG. 2, in some embodiments the signal source(s) 28 maybe embodied as a number of magnetic sources, such as permanent magnets,as discussed above in regard to FIG. 1. The magnetic signal source(s) 28may be coupled to one or more components of the orthopaedic prosthesis12 and/or one or more relevant bones of the patient 16. In suchembodiments, the sensor array 28 is embodied as a magnetic sensor array60. The magnetic sensor array 60 is formed from a number of magneticsensors, which may be positioned in a predetermined configuration tothereby sense or measure one or more components of the three dimensionalmagnetic field generated by the magnetic signal source(s) 28. Theparticular number of magnetic sensors used to form the magnetic sensorarray 60 may depend on such criteria as the type of magnetic sensors,the specific application, and/or the configuration of the magneticsensor array 60. The magnetic sensor array 60 may include any number andconfiguration of one-dimensional, two-dimensional, and/orthree-dimensional magnetic sensors such that the magnetic sensor array60 is capable of sensing or measuring the magnetic field of the magneticsignal source(s) 28 implanted in the patient 16 when the patient isstanding on the patient support platform 18. Additionally, the magneticsensor(s) may be embodied as any type of magnetic sensor capable ofsensing or measuring the magnetic field generated by the magnetic signalsource 28. For example, the magnetic sensors may be embodied as one ormore superconducting quantum interference (SQUID) magnetic sensors,anisotropic magnetoresistive (AMR) magnetic sensors, giantmagnetoresistive (GMR) magnetic sensors, Hall-effect magnetic sensors,or any other type of magnetic sensors capable of sensing or measuringthe three-dimensional magnetic field of the magnetic source.

As such, the magnetic sensor array 60 may be embodied as any type ofmagnetic sensor array capable of sensing or measuring a magnetic fieldgenerated by the magnetic signal source(s) 28. For example, the magneticsensor array 60 may be embodied as one of the magnetic sensor arraysdescribed in detail in U.S. patent application Ser. No. 11/323,609,entitled “APPARATUS AND METHOD FOR REGISTERING A BONE OF A PATIENT WITHA COMPUTER ASSISTED ORTHOPAEDIC SURGERY SYSTEM”, which was filed on Dec.30, 2005 by Jason T. Sherman et al.; in U.S. patent application Ser. No.11/323,963, entitled “SYSTEM AND METHOD FOR REGISTERING A BONE OF APATIENT WITH A COMPUTER ASSISTED ORTHOPAEDIC SURGERY SYSTEM,” which wasfiled on Dec. 30, 2005 by Jason T. Sherman et al.; in U.S. patentapplication Ser. No. 11/323,610, entitled “MAGNETIC SENSOR ARRAY,” whichwas filed on Dec. 30, 2005 by Jason T. Sherman et al.; and/or in U.S.patent application Ser. No. 11/323,537, entitled “METHOD FOR DETERMININGA POSITION OF A MAGNETIC SOURCE,” which was filed on Dec. 30, 2005 byJason T. Sherman et al., the entirety of all of which is expresslyincorporated herein by reference.

In the illustrative embodiment of FIG. 2, the magnetic sensor array 60is coupled to the support frame 20 and the patient support platform 18.The magnetic sensor array 60 is centrally located on the surface 22 ofthe patient support platform 18 such that the magnetic sensor array 60is positioned between the legs of the patient 16 while the patient 16 isstanding on the patient support platform 18. In this way, the magneticsensor array 60 is positioned in a location for sensing the magneticfield(s) generated by the magnetic signal source(s) 28 located in theregion of the knee of the patient 16. For example, the apparatus 14illustrated in FIG. 2 may be used in embodiments wherein the orthopaedicprosthesis 12 is embodied as a knee prosthesis. In other embodiments,such as those embodiments wherein the orthopaedic prosthesis 12 isembodied as a hip prosthesis or a shoulder prosthesis, the magneticsensor array 60 may be coupled to the patient support platform 18 andsupport frame 20 in a different location. For example, in embodimentswherein the orthopaedic prosthesis 12 is embodied as a hip prosthesis,the magnetic sensor array 60 may be coupled a side rail 62, 64 of thesupport frame 20 in an elevated position relative to the magnetic sensorarray 60 illustrated in FIG. 2. Additionally, the apparatus 14 mayinclude more than one magnetic sensor arrays 60 in some embodiments. Forexample, the apparatus 14 may include a magnetic sensor array 60 coupledto each of the side rails 62, 64. Additionally or alternatively, themagnetic sensor array 60 may be configured to be positionable in one ora number of locations on the support frame 20 and/or patient supportplatform 18 such that the magnetic sensor array 60 may be relocatedbased on the type of orthopaedic prosthesis 12 being monitored.

Referring now to FIG. 3, in some embodiments the signal source(s) 28 maybe embodied as a number of wireless transmitters as discussed above inregard to FIG. 1. The wireless transmitters may be coupled to one ormore components of the orthopaedic prosthesis 12 and/or one or morerelevant bones of the patient 16. The wireless transmitters may beconfigured to transmit a wireless signal at a predetermined frequency ora predetermined pulse repetition frequency. In some embodiments, thewireless signal generated by the wireless transmitters is anon-modulated wireless signal. That is, the wireless signal does notinclude other signals (e.g., data signals) embedded or modulated in thepredetermined carrier frequency. In other embodiments, the wirelesssignal generated by the wireless transmitters is a modulated wirelesssignal having a serial number associated with the wireless transmittedmodulated on a predetermined carrier frequency. The predeterminedfrequency of the wireless signal may be any frequency receivable by thesensor array 26 such as, for example, a frequency or range offrequencies in the very-high frequency (VHF) band or ultra-highfrequency (UHF) band.

In such embodiments, the sensor array 26 is embodied as an antenna array70. The antenna array 70 includes a number of coplanar antennas 72, 74,76 and at least one non-coplanar antennas 78 (with respect to thecoplanar antennas 72, 74, 76). The antennas 72, 74, 76, 78 aredirectional antennas having a radiation/receiving pattern that is notomni-directional. For example, the antennas 72, 74, 76, 78 may beunidirectional antennas. In one particular embodiment, the antennas 72,74, 76, 78 are spiral directional antennas. The directivity of eachdirectional antenna 72, 74, 76, 78 is defined by the beamwidth theantenna 72, 74, which is defined about the boresight of each antenna 72,74, 76, 78. The boresight of the antenna 72, 74, 76, 78 typicallycorresponds to a physical axis of the antenna and is defined as the axisof the antenna 72, 74, 76, 78 along which the gain of the antenna 72,74, 76, 78 is greatest. As such, the antennas 72, 74, 76, 78 aresensitive to signals generated by sources positioned in the antenna's72, 74, 76, 78 beamwidth. Conversely, signals incoming toward theantennas 72, 74, 76, 78 from sources outside of the beamwidth of theantennas 72, 74, 76, 78 are substantially attenuated.

As such, the antenna array 70 may be embodied as any type of antennaarray having a number of co-planar antennas and at least onenon-coplanar antenna. For example, the antenna array 70 may be embodiedas one of the antenna arrays described in detail in U.S. patentapplication Ser. No. 11/391,840, entitled “SYSTEM AND METHOD FORDETERMINING A LOCATION OF AN ORTHOPAEDIC MEDICAL DEVICE,” which wasfiled on Mar. 29, 2006 by Edward J. Caylor III, et al. and/or in U.S.patent application Ser. No. 11/392,001, entitled “SYSTEM AND METHOD FORMONITORING KINEMATIC MOTION OF A PATIENT,” which was filed on Mar. 29,2006 by Edward J. Caylor III, the entirety of each of which is expresslyincorporated herein by reference.

In the illustrative embodiment of FIG. 3, the coplanar antennas 72, 74,76 and the non-coplanar antenna 78 are coupled to the support frame 20of the apparatus 14. To do so, the antennas 72, 74, 76, 78 arepositioned in housings 80, 82, 84, 86, respectively, which are coupledto a frame 20 of the patient support apparatus 14. That is, the firsthousing 80, and thereby the coplanar antenna 72, is coupled to thesupport frame 20 of the patient support apparatus 14 on a firstlongitudinal side 88. The second housing 82, and thereby the coplanarantenna 74, is coupled to the support frame 20 on a second longitudinalside 90 of the patient support apparatus 14. The third housing 84, andthereby the coplanar antenna 76, is coupled to the support frame 20 on afront side 92 of the patient support apparatus 14. The housings 80, 82,84 are coupled to the support frame 20 such that the antennas 72, 74, 76are positioned coplanar with respect to each other. Additionally, theantennas are positioned such that the boresight of each antenna 72, 74,76 is directed inwardly toward the area of the patient support platform18 wherein the patient 16 is to stand. That is, the antenna 72 ispositioned such that the boresight of the antenna 72 is directed towardthe opposite longitudinal side 90 of the patient support apparatus 14.Similarly, the antenna 74 is positioned such that the boresight of theantenna 74 is directed toward the opposite longitudinal side 88. Theantenna 76 is positioned such that the boresight of the antenna 76 isdirected toward a rear side 94 of the patient support apparatus 14.

The beamwidths of the antennas 72, 74, 76 define a common volume ofspace in which the relevant portion(s) of the patient 16 (i.e., theportion of the patient 16 wherein the orthopaedic prosthesis 12 isimplanted) is positioned when the patient 16 is supported by the patientsupport platform 18. For example, if the relevant portion of the patientis a knee area, the antennas 72, 74, 76 are positioned such that therelevant knee and surrounding area of the patient 16 is positioned inthe common volume of space defined by the beamwidths of the antennas 72,74, 76. To facilitate various areas of interest of the patient 16, insome embodiments, the housings 80, 82, 84 are movably coupled to thesupport frame 20 such that the housings 80, 82, 84 may be moved todifferent positions to thereby move the common volume of space such thatthe relevant portion of the patient 16 is positioned therein. Forexample, the housings 80, 82, 84 may be movably coupled to the supportframe 20 such that the housings 80, 82, 84 may be moved vertically up ordown as required based on the location of the orthopaedic prosthesis 12.

The housing 86 is also coupled to the support frame 20. The housing 86is so coupled such that the antenna 78 is positioned non-coplanar withrespect to the antennas 72, 74, 76 but is directed toward the referenceplane defined by the antennas 72, 74, 76. That is, the antenna 78 iscoupled to the support frame 20 such that the beamwidth of the antenna78 is directed toward the common volume of space defined by thebeamwidths of the antennas 72, 74, 76. Similar to the housings 80, 82,84, the housing 86 may be movably coupled to the support frame 20 suchthat the housing 86 may be moved to different positions to thereby movethe common volume of space such that the relevant portion of the patient16 is positioned therein.

Referring now to FIG. 4, in some embodiments, the apparatus 14 mayinclude a jig 100 for securing the patient 16, or a portion of thepatient 16 such as a leg, in a fixed position relative to the patientsupport apparatus 14. Depending on the particular location of theorthopaedic prosthesis 12 in the patient 16, the jig 100 or componentsthereof may be movably secured to the patient support apparatus 14 in anumber of locations. In one particular embodiment, as illustrated inFIG. 4, the jig 100 is embodied as a number of pads 102 movably coupledto the support frame 20 such that each pad 102 is extendable relative tothe support frame 20. Each of the pads 102 includes a substrate 104 anda padding surface 106. The substrate 104 may be formed from any materialrigid enough to support the padding surface 106 in a compressed stateagainst the body of the patient 16. The pads 102 are movably coupled tothe support frame 20 via a number of threaded screws 108. The pads 102may be extended from or toward the support frame 20 by adjusting thescrews 108. In this way, the patient 16, or portion of the patient 16such as a leg, may be secured in a fixed position by adjusting thescrews 108 to extend the pads 102 toward the body of the patient 16.Because both sets of pads 102 are extendible toward each other, the pads102 may be extended until each pad 102 applies enough pressure on thebody of the patient 16 to secure the relevant portion of the patient 16in a fixed position.

It should be appreciated that in embodiments wherein the controller 30is configured to determine the position of the orthopaedic prosthesis12, or component thereof, the relevant portion of the patient 16 issecured in a fixed position that is similar to the position of thepatient during previous examinations. In this way, any change in theposition of the orthopaedic prosthesis 12 is attributable to a change inthe position of the prosthesis 12 relative to the patient rather than achange in the position of the patient 16 relative to the patient supportplatform 18.

Although the jig 100 is illustrated and described as a number of movablepads in regard to FIG. 4, it should be appreciated that other jigs maybe used to secure the patient 16, or portion thereof, in a fixedposition relative to the platform 18 in other embodiments. For example,a number of straps may be used to secure a portion, such as a leg, ofthe patient 16 in a fixed position relative to the patient supportapparatus 14. In other embodiments, the jig 100 may be embodied as abrace such as a leg brace, a receptacle configured to receive therelevant portion of the patient, and/or the like. Additionally, in someembodiments, the top surface 22 of the patient support platform 18 mayinclude markings or other indications of the location in which thepatient is to stand (e.g., the location in which the patient 16 shouldplace his/her feet).

Referring now to FIG. 5, in embodiments wherein the controller 30 isconfigured to determine the position of the orthopaedic prosthesis 12relative to the patient support apparatus 14 (e.g., relative to thepatient support platform 18 or the sensor array 26), the controller 30may be configured to execute an algorithm 200 for determining theposition of the orthopaedic prosthesis 12 or component(s) thereof. Insuch embodiments, each component of interest of the orthopaedicprosthesis 12 includes one or more signal sources 28 coupled thereto. Asdiscussed above in regard to FIGS. 1-3, such signal sources 28 may beembodied as a number of magnetic sources or a number of wirelesstransmitters.

The algorithm 200 beings with a process step 202 in which the controller30 determines if the patient 16 has mounted the patient support platform18. To do so, the patient support platform 18 may include a number ofsensors, such as pressure sensors, for detecting when the patient 16 hasmounted the platform 18. Alternatively, the orthopaedic healthcareprovider may instruct the controller 30 that the patient hassuccessfully mounted the patient support platform 18 by, for example,selecting an appropriate button, entering a predetermined command, orthe like via the input device 46.

Once the controller 30 has determined that the patient 16 has mountedthe patient support platform 18, the patient 16 is secured in a fixedposition on the platform 18 in process step 204. That is, the portion ofthe patient 16 wherein the orthopaedic prosthesis 12 and/or any bone(s)of interest are located is secured in a fixed position relative to thepatient support apparatus 14. To do so, the jig 100 may be used tosecure the patient 16. For example, in embodiments wherein the jig 100is embodied as the pads 102 illustrated in FIG. 4, the screws 108 may beoperated to extend the pads 102 in an outward direction relative to thesupport frame 20 to thereby apply a securing pressure on the relevantportion of the patient 16. As discussed above in regard to FIG. 4, othertypes of jigs 100, such as straps, braces, and/or the like, may be usedto secure the patient 16 in other embodiments.

Once the relevant portion of the patient 16 has been secured in a fixedposition in process step 204, the sensor array 26 receives the outputsignals from the signal source(s) 28 coupled to the orthopaedicprosthesis 12. As discussed above in regard to FIG. 2, the sensor array26 may be embodied as a magnetic sensor array 60 configured to sense ordetect a magnetic field(s) generated by a magnetic signal source(s) 28.Alternatively, as discussed above in regard to FIG. 3, the sensor array26 may be embodied as an antenna array 70 configured to receive outputsignals from a wireless transmitter signal source(s) 28. In someembodiments, such wireless transmitter signal source(s) 28 may beconfigured to transmit the output signals only while being inductivelypowered. In such embodiments, the patient support apparatus 14 mayinclude a primary coil or the like to power the wireless transmittersignal source(s) 28. The primary coil may be controlled by, for example,the controller 30. Regardless, the output signals generated by thesignal source(s) 28 are received by the sensor array 26 in process step206.

Once the sensor array 26 receives the output signals from the signalsource(s) 28, the controller 30 determines the position of theorthopaedic prosthesis 12, or component(s) thereof, relative to thepatient support apparatus 14 in process step 208. To do so, thecontroller 30 receives data signals from the sensor array 26 indicativeof the position of the orthopaedic prosthesis 12 relative to the sensorarray 26. The controller 30 is configured to determine the position ofthe orthopaedic prosthesis 12 based on such data signals. The controller30 may use any suitable algorithm to determine the position of theorthopaedic prosthesis 12. For example, in embodiments wherein thesensor array 26 is embodied as a magnetic sensor array 60, thecontroller 30 may be configured to execute an optimization algorithm.That is, the controller 30 may determine an initial estimate of theposition (e.g., the six degrees of freedom) of the magnetic signalsource(s) 28, determine theoretical magnetic field components of thethree-dimensional magnetic flux density of the magnetic signal source(s)28 based on the estimated position, and calculate the sum of errorsbetween the theoretical magnetic field components and the measuremagnetic field components of the magnetic signal source as measured bythe magnetic sensor array 60. Such a calculation process may then berepeated using an adjusted estimated position of the magnetic signalsource(s) 28 until the sum of errors is less than some predeterminedthreshold value. Once the sum of errors is less than the predeterminedthreshold value, the position of the magnetic signal source(s) has beendetermined. Because the position of the magnetic sensor array 60relative to the patient support apparatus 14 is known, the position ofthe magnetic signal source(s) 28 relative to the patient supportapparatus 14 may be determined by extrapolation.

One example of such an optimization algorithm which may be used by thecontroller 30 to determine the position of the magnetic signal source(s)is described in detail in U.S. patent application Ser. No. 11/323,609,entitled “APPARATUS AND METHOD FOR REGISTERING A BONE OF A PATIENT WITHA COMPUTER ASSISTED ORTHOPAEDIC SURGERY SYSTEM”, which was filed on Dec.30, 2005 by Jason T. Sherman et al.; in U.S. patent application Ser. No.11/323,963, entitled “SYSTEM AND METHOD FOR REGISTERING A BONE OF APATIENT WITH A COMPUTER ASSISTED ORTHOPAEDIC SURGERY SYSTEM,” which wasfiled on Dec. 30, 2005 by Jason T. Sherman et al.; in U.S. patentapplication Ser. No. 11/323,610, entitled “MAGNETIC SENSOR ARRAY,” whichwas filed on Dec. 30, 2005 by Jason T. Sherman et al.; and in U.S.patent application Ser. No. 11/323,537, entitled “METHOD FOR DETERMININGA POSITION OF A MAGNETIC SOURCE,” which was filed on Dec. 30, 2005 byJason T. Sherman et al., the entirety of all of which is expresslyincorporated herein by reference.

Alternatively, in embodiments wherein the sensor array 26 is embodied asan antenna array 70, the controller 30 may be configured to execute aradio frequency (RF) direction finding algorithm. Because each of thecoplanar antennas 72, 74, 76 and non-coplanar antenna 78 is positionedat a different location with respect to the orthopaedic prosthesis(i.e., with respect to the wireless transmitter signal source(s) 28coupled to the prosthesis 12), the data signals received from eachantenna 72, 74, 76, 78 are different to varying amounts. As such, thelocation of the wireless transmitter signal source(s) 28, and thereforethe location of the orthopaedic prosthesis 12, may be determined bycomparing a portion or all of the data signals received form theantennas 72, 74, 76, 78. To do so, the controller 30 may use any radiofrequency direction finding algorithm capable of determining dataindicative of the location of the wireless transmitter signal source(s)28 based on the data signals received from the antenna array 70. Forexample, the controller 30 may determine the location of the wirelesstransmitter signal source(s) 28 by comparing or otherwise analyzing theamplitudes of the various data signals, the phase of the data signals,the Doppler frequency shift of the data signals, the differential timeof arrival of the data signals, and/or any other radio frequencydirection finding methodology usable to determine the location of thewireless transmitter signal source(s) 28.

One example of such a algorithm for determining the position of theorthopaedic prosthesis 12 (i.e., the wireless transmitter signalsource(s) 28) is described in detail in U.S. patent application Ser. No.11/391,840, entitled “SYSTEM AND METHOD FOR DETERMINING A LOCATION OF ANORTHOPAEDIC MEDICAL DEVICE,” which was filed on Mar. 29, 2006 by EdwardJ. Caylor III, et al. and in U.S. patent application Ser. No.11/392,001, entitled “SYSTEM AND METHOD FOR MONITORING KINEMATIC MOTIONOF A PATIENT,” which was filed on Mar. 29, 2006 by Edward J. Caylor III,the entirety of each of which is expressly incorporated herein byreference.

Once the position (e.g., the location and orientation) of theorthopaedic prosthesis 12 (i.e., the position of the signal source(s)28) has been determined in process step 208, data indicative of suchposition(s) is stored in process step 210. The position data may bestored, for example, in the memory device 38. Additionally oralternatively, the position data may be transferred to and stored in thedatabase 40 via the communication links 42. Once the position data hasbeen stored, the controller 30 displays indicia of the position of theorthopaedic prosthesis 12, or components thereof, on the display device24 and/or the display device 48 in process step 212. The controller 30displays the indicia of the position of the orthopaedic prosthesis 12relative to the patient support platform 18. Such indicia may beembodied as, for example, a graph, table, a number of images, datavalues, and/or the like. In one particular embodiment, the controller 30is configured to display an image of the orthopaedic prosthesis 12 in alocation and orientation determined based on the position data.

Once indicia of the position of the orthopaedic prosthesis 12, orcomponents thereof, has been displayed in process step 212, thecontroller 30 determines if the orthopaedic healthcare provider desiresto display historical position data. The orthopaedic healthcare providermay instruct the controller 30 to display the historical position databy supplying the appropriate commands via the remote control panel 44.Alternatively, the controller 30 may be configured to always display thehistorical position data. If the controller 30 determines that theorthopaedic healthcare provider does not desire to display thehistorical position data, the algorithm 200 loops back to process step202. However, if the controller 30 is configured or instructed todisplay the historical position data, the algorithm 200 advances toprocess step 216 in which the controller 30 retrieves the historicalposition data from a storage device. For example, the controller 30 mayretrieve the historical position data form the database 40. It should beappreciated that the historical position data is embodied as dataindicative of the position of the orthopaedic prosthesis 12 and/orrelevant bones of the patient 16 as determined during one or moreprevious examinations using the system 10.

Once the controller 30 has retrieved the historical position data of theorthopaedic prosthesis 12, or components thereof, the controller 30 isconfigured to display indicia of the historical position(s) of theorthopaedic prosthesis 12 on the display device 24 and/or display device48. The indicia of the historical position(s) may be displayedcontemporaneously with the indicia of the present position of theorthopaedic prosthesis 12 such that the orthopaedic healthcare providermay perform a comparison between the historical potions(s) and presentposition of the orthopaedic prosthesis 12 to determine the presence andextent of any implant migration and/or subsidence. In addition, theindicia of the historical position(s) may be displayed in a manner toidentify that the data is historical rather than present. For example,the indicia of the historical position(s) of the orthopaedic prosthesis12 may be displayed in a color or configuration that is different fromthe indicia of the present position of the prosthesis 12.

Referring now to FIG. 6, in embodiments wherein the controller 30 isconfigured to determine the position of individual components of theorthopaedic prosthesis 12 (e.g., a tibial component and a femoralcomponent of an orthopaedic knee prosthesis) relative to each other, thecontroller 30 may be configured to execute an algorithm 300 fordetermining the position of the components of the orthopaedic prosthesis12. In such embodiments, each component of interest of the orthopaedicprosthesis 12 includes one or more signal sources 28 coupled thereto. Asdiscussed above in regard to FIGS. 1-3, such signal sources 28 may beembodied as a number of magnetic sources or a number of wirelesstransmitters.

The algorithm 300 beings with a process step 302 in which the controller30 determines if the patient 16 has mounted the patient support platform18. As discussed above in regard to algorithm 200, the patient supportplatform 18 may include a number of sensors for detecting when thepatient 16 has mounted the platform 18 and/or the controller 30 may beinstructed that the patient 16 has successfully mounted the platform 18by the orthopaedic healthcare provider. Once the controller 30 hasdetermined that the patient 16 has mounted the patient support platform18, the patient 16 is secured in a fixed position on the platform 18 inprocess step 304. The patient 16 is secured in the fixed position viause of the jigs 100 as discussed above in regard to process step 204 ofalgorithm 200. The sensor array 26 subsequently receives the outputsignals from the signal source(s) 28 coupled to the individualcomponents of the orthopaedic prosthesis 12 in process step 306. Again,as discussed above in regard to FIG. 2, the sensor array 26 may beembodied as a magnetic sensor array 60 configured to sense or detect amagnetic field(s) generated by a magnetic signal source(s) 28 or anantenna array 70 configured to receive output signals from a wirelesstransmitter signal source(s) 28 as discussed above in regard to FIG. 3.

Once the sensor array 26 receives the output signals from the signalsource(s) 28, the controller 30 determines the position of each relevantcomponent of the orthopaedic prosthesis 12 relative to each other inprocess step 308. To do so, the controller 30 receives data signals fromthe sensor array 26 indicative of the position of the components of theorthopaedic prosthesis 12 relative to the sensor array 26. Thecontroller 30 is configured to determine the position of each relevantcomponent of the orthopaedic prosthesis 12 based on such data signals.The controller 30 may use any suitable algorithm to determine theposition of the components of the orthopaedic prosthesis 12. Forexample, in embodiments wherein the sensor array 26 is embodied as amagnetic sensor array 60, the controller 30 may be configured to executean optimization algorithm as discussed in more detail above in regard toprocess step 208 of algorithm 200. Alternatively, in embodiments whereinthe sensor array 26 is embodied as an antenna array 70, the controller30 may be configured to execute a radio frequency (RF) direction findingalgorithm as also discussed above in regard to process step 208 ofalgorithm 200. Regardless, the controller 30 determines the position ofeach component of the orthopaedic prosthesis 12 relative to each other.

Once the controller 30 has determined the position of each relevantcomponent, the controller 30 is configured to store data indicative ofsuch positions in process step 310. The position data may be stored, forexample, in the memory device 38 and/or database 40. Because thecontroller 30 is configured to determine the position of each componentrelative to each other, the controller 30 may store the position data ina relative form. For example, the controller 30 may store position datafor an initial component and store position data for each subsequentcomponent in a data form relative to the initial form such as, forexample, in a vector format. Once the position data has been stored, thecontroller 30 displays indicia of the position of each relevantcomponent of the orthopaedic prosthesis relative to each other on thedisplay device 24 and/or the display device 48 in process step 312. Suchindicia may be embodied as, for example, a graph, table, a number ofimages, data values, and/or the like.

Once indicia of the position of the orthopaedic prosthesis 12, orcomponents thereof, has been displayed in process step 312, thecontroller 30 determines if the orthopaedic healthcare provider desiresto display historical position data in process step 314. If so, thealgorithm 300 advances to process step 316 in which the controller 30retrieves the historical position data from a storage device such as,for example, the memory device 38 and/or the database 40. Again, thehistorical position data is embodied as data indicative of the positionof the components of the orthopaedic prosthesis 12 as determined duringone or more previous examinations using the system 10.

Once the controller 30 has retrieved the historical position data of therelevant components of the orthopedic prosthesis 12, the controller 30is configured to display indicia of the historical position(s) of theorthopaedic prosthesis 12 components on the display device 24 and/ordisplay device 48. The indicia of the historical position(s) may bedisplayed contemporaneously with the indicia of the present position ofthe components of the orthopaedic prosthesis 12 such that theorthopaedic healthcare provider may perform a comparison between thehistorical position(s) and present position of the components todetermine the presence and extent of any implant migration and/orsubsidence.

Referring now to FIG. 7, in embodiments wherein the controller 30 isconfigured to determine the position of the orthopaedic prosthesis 12,or components thereof, relative to the bone(s) of the patient 16, thecontroller 30 may be configured to execute an algorithm 400 fordetermining the position of the orthopaedic prosthesis 12 and relevantbone(s) of the patient 16. In such embodiments, each component ofinterest of the orthopaedic prosthesis 12 and each relevant bone of thepatient 16 includes one or more signal sources 28 coupled thereto. Asdiscussed above in regard to FIGS. 1-3, such signal sources 28 may beembodied as a number of magnetic sources or a number of wirelesstransmitters.

The algorithm 400 beings with a process step 402 in which the controller30 determines if the patient 16 has mounted the patient support platform18. As discussed above in regard to algorithm 200, the patient supportplatform 18 may include a number of sensors for detecting when thepatient 16 has mounted the platform 18 and/or the controller 30 may beinstructed that the patient 16 has successfully mounted the platform 18by the orthopaedic healthcare provider. Once the controller 30 hasdetermined that the patient 16 has mounted the patient support platform18, the patient 16 is secured in a fixed position on the platform 18 inprocess step 404. The patient 16 is secured in the fixed position viause of the jig 100 as discussed above in regard to process step 204 ofalgorithm 200. The sensor array 26 subsequently receives the outputsignals from the signal source(s) 28 coupled to the individualcomponents of the orthopaedic prosthesis 12 in process step 406. Again,as discussed above in regard to FIG. 2, the sensor array 26 may beembodied as a magnetic sensor array 60 configured to sense or detect amagnetic field(s) generated by a magnetic signal source(s) 28 or anantenna array 70 configured to receive output signals from a wirelesstransmitter signal source(s) 28 as discussed above in regard to FIG. 3.

Once the sensor array 26 receives the output signals from the signalsource(s) 28, the controller 30 determines the position (i.e., locationand orientation) of each relevant bone of the patient 16 (e.g., eachbone having one or more components of the orthopaedic prosthesis 12coupled thereto). To do so, the controller 30 receives data signals fromthe sensor array 26 indicative of the position of the relevant bone(s)of the patient 16 relative to the sensor array 26. The controller 30 isconfigured to determine the position of each relevant component of theorthopaedic prosthesis 12 based on such data signals. The controller 30may use any suitable algorithm to determine the position of the bone(s)of the patient 16 such as the optimization algorithm or radio frequency(RF) direction finding algorithm described above in regard to FIGS. 2and 3 respectively depending upon the particular embodiment of thesensor array 26. Once the controller 30 has determined the position ofthe relevant bone(s) of the patient 16, the controller 30 determines theposition of the relevant components of the orthopaedic prosthesis 12 inprocess step 410. The controller 30 is configured to determine theposition of the components of the prosthesis 12 relative to the positionof the relevant bone(s) of the patient 16. Similar to process step 308of algorithm 300, the controller 30 may use any suitable algorithm todetermine the position(s) of the relevant components of the orthopaedicprosthesis 12.

Once the controller 30 has determined the position of each relevant boneand orthopaedic prosthesis 12 components, the controller 30 isconfigured to store data indicative of such positions in process step412. The position data may be stored, for example, in the memory device38 and/or database 40. Again, as discussed above in regard to processstep 310 of algorithm 300, the controller 30 may store the position datain a relative form. For example, the controller 30 may store theposition data for the component(s) of the orthopaedic prosthesis 12 in arelative form or format based on the position of the relevant bone(s) ofthe patient 16 as determined in process step 408. Once the position datahas been stored, the controller 30 displays indicia of the position ofeach relevant bone of the patient 16 on the display device 24 and/or thedisplay device 48 in process step 414. In addition, the controller 30also displays indicia of the position of each relevant component of theorthopaedic prosthesis 12 in process step 414. The controller 30displays the indicia of the positions of the components of theorthopedic prosthesis 12 relative to the relevant bone(s) of the patient16. Such indicia may be embodied as, for example, a graph, table, anumber of images, data values, and/or the like.

Once indicia of the positions of the relevant bones and orthopaedicprosthesis 12 components has been displayed in process step 414, thecontroller 30 determines if the orthopaedic healthcare provider desiresto display historical position data in process step 416. If so, thealgorithm 400 advances to process step 416 in which the controller 30retrieves the historical position data from a storage device such as,for example, the memory device 38 and/or the database 40. Again, thehistorical position data is embodied as data indicative of the positionof the components of the orthopaedic prosthesis 12 as determined duringone or more previous examinations using the system 10.

Once the controller 30 has retrieved the historical position data of therelevant components of the orthopedic prosthesis 12, the controller 30is configured to display indicia of the historical position(s) of therelevant bone(s) of the patient 16 and the relevant components of theorthopaedic prosthesis 12 on the display device 24 and/or display device48. The indicia of the historical position(s) may be displayedcontemporaneously with the indicia of the present position of thebone(s) of the patient 16 and the components of the orthopaedicprosthesis 12 such that the orthopaedic healthcare provider may performa comparison between the historical position(s) and present position ofthe components o determine the presence and extent of any implantmigration and/or subsidence.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the systems, apparatuses, and methodsdescribed herein. It will be noted that alternative embodiments of thesystems and methods of the present disclosure may not include all of thefeatures described yet still benefit from at least some of theadvantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations of the systems, apparatuses,and methods that incorporate one or more of the features of the presentinvention and fall within the spirit and scope of the present disclosureas defined by the appended claims.

1. An apparatus for monitoring the position of an orthopaedic prosthesis implanted in a body of a patient, the apparatus comprising: a patient support platform configured to support a patient in a standing position, the patient support platform including a top planar surface; a sensor array coupled to the patient support platform and configured to generate data signals in response to an output signal received from a signal source coupled to the orthopaedic prosthesis implanted in the body of the patient while the patient is supported by the patient support platform in the standing position, the sensory array including (i) a first directional antenna having a first boresight, (ii) a second directional antenna having a second boresight, (iii) a third directional antenna having a third boresight, each of the first, second, and third boresights being coplanar with each other, and (iv) a fourth directional antenna having a fourth boresight that is non-coplanar with the first, second, and third boresights, each of the first, second, third, and fourth boresights being directed toward a common volume of space; a jig coupled to the patient support platform and comprising a first patient securing member located a first distance above the patient support platform and a second securing member located a second distance above the patient support platform substantially equal to the first distance, the first and second patient securing members being positionable to apply pressure in opposing directions to a portion of the body of the patient to secure the portion of the body of the patient (i) in a fixed position relative to the sensor array and (ii) within the common volume while the patient is standing on the patient support platform, the portion of the body of the patient having the orthopaedic prosthesis implanted therein; and a controller electrically coupled to the sensor array and configured to determine the position of the orthopaedic prosthesis based on the data signals received from the sensor array.
 2. The apparatus of claim 1, wherein the patient support platform comprises an enclosure and at least a portion of the controller is positioned in the enclosure.
 3. The apparatus of claim 1, wherein each of the first, second, third, and fourth directional antennas is configured to generate data signals in response to an output signal received from a wireless transmitter coupled to the orthopaedic prosthesis.
 4. The apparatus of claim 1, wherein the first, second, third, and fourth directional antennas are spiral directional antennas.
 5. The apparatus of claim 1, wherein the controller is configured to determine the position of the orthopaedic prosthesis by comparing the data signals to each other.
 6. The apparatus of claim 1 further comprising a display device coupled to the patient support platform and electrically coupled to the controller, wherein the controller is configured to display indicia of the location of the orthopaedic prosthesis on the display device.
 7. The apparatus of claim 6, wherein the controller is further configured to retrieve position data indicative of a previously determined position of the orthopaedic prosthesis from a storage device and display indicia of the previously determined position of the orthopaedic prosthesis on the display device.
 8. The apparatus of claim 1, wherein the first boresight, the second boresight, the third boresight, and the fourth boresight intersect each other in the common volume of space.
 9. The apparatus of claim 1, wherein the first, second, and third directional antennas are coupled to the patient support platform such that when the patient is supported by the patient support platform in the standing position: the first directional antenna is located in front of the patient, the second directional antenna is located toward the left side of the patient, and the third directional antenna is located toward the right side of the patient.
 10. The apparatus of claim 8, wherein the fourth directional antenna is coupled to the patient support platform such that the fourth directional antenna is located in front of the patient when the patient is supported by the patient support platform in the standing position. 